abstract

The paper presented damage localization of plate-like structures using stationary wavelet transform (SWT) of displacement mode shapes. SWT is a redundant transform which doubles the number of input samples at each iteration. It provides a more accurate estimation of the variances and facilitates the identification of salient features in a signal, especially for recognizing noise or signal rupture. The displacement mode shapes of a cracked plate that contains a crack of small depth are essentially smooth surfaces. In reality, the mode shapes contain very small local peaks or discontinuities in the region of damage. However, it is difficult to identify and locate a crack directly from the graphical plot of the displacement mode shapes. Using SWT, mode shape curves can be decomposed into smooth, low order curves, called approximation coefficients, and wavy, high order curves called the detail coefficients, which include defect information that is useful for damage localization. The modal responses of the damaged fixed plates with a small crack ratio of 5% were computed using the finite element method (FEM). The results show that the SWT-based method has great potential in damage localization of plate-like structures as it does not require the modal parameter of an intact plate as a baseline for damage localization. Therefore, it can be recommended for real applications.

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